One of the common uses of oil flooded screw compressors is on portable blast hole drills to provide air to bail the cuttings out of the hole and to cool the drill bit. Blast hole drills are frequently used in strip mining operations that are often located in geographical areas having very cold climates. In such installations, the compressor and air/oil reservoir are installed in a heated machinery house on the drill while the oil cooling radiator or cooler is located outside the house where it is exposed to large volumes of cool atmospheric air which are required to cool the oil.
During extended shutdown periods in subzero temperatures, the oil thickens in the radiator and in the connecting lines which are located outside of the heated machinery house on the drill. The oil may then be too thick to flow properly through the exterior radiator and connecting lines when the thermostatic control valve opens shortly after start-up, thus preventing flow of cooled lubricating oil to the compression chamber. An excess air/oil mixture temperature will result in the compressor shutting down after running only a few minutes. To avoid this problem, in the past portable heaters were used to heat the oil in the exterior radiator or cooler and in the connecting lines causing substantial delays in restarting the compressor.
The oil purge system of this invention is designed to prevent the cold weather start-up problems for such compressors and avoids having to apply supplemental heat to the oil cooling radiator and connecting lines and the attendant downtime of the compressor.
Therefore, it is a primary object of this invention to provide an oil purge system for the oil cooling radiator and connecting lines of a flooded type screw compressor.